A Subgigahertz UWB Transmitter With Wireless Clock Harvesting for RF-Powered Applications

Abstract

A subgigahertz ultrawideband (UWB) transmitter (TX) with wireless clock harvesting is presented for RF-powered applications such as RF identifications and implantable devices in the 180-nm CMOS process. The proposed low-power TX consists of a harmonic injection-locked ring oscillator (ILRO), a synchronized pulse generator, and a driver stage. Through wireless injection locking, a 450-MHz carrier is extracted using the subharmonic of an ultrahigh frequency signal radiated by a reader. Following the ILRO, the carrier is gated and amplified to generate the UWB pulses. This approach avoids power-hungry frequency synthesis circuitry and bulky crystal reference, and it relaxes the timing synchronization between the reader and the tag. Due to aggressive duty cycling and the fast setup time (<; 50 ns at an input power of -15 dBm), the proposed TX is power scalable with an energy consumption of 35 pJ/pulse. To comply with the Federal Communications Commission regulations, the maximum pulse rate is up to 5 MHz with a peak-to-peak pulse amplitude of 0.75 V and a corresponding power consumption of 175 μW, which is favorable to RF-powered applications.